The reason people put larger props when moving up to diesel is the increase in power.

You should beable to increase the pitch instead of the length to better use the extra power.

Dare I say that most who run diesel want more power but not more speed
that is why they go with the longer prop.

I have mixed feelings on the tuned exhaust.
I don't believe you would get as much gain as with non-diesel engines,
because of the more effecent combustion.
But you start off with more anyway.

Just my 2 cents worth.